Step1 In O2 ; we have 2 unpaired electrons which occupy pi 2p * Anti bonding orbital. Hence O2 molecule is paramagnetic. Step2 C2^- has 1 unpaired electron; is also paramagnetic. Solution Step1 In O2 ; we have 2 unpaired electrons which occupy pi 2p * Anti bonding orbital. Hence O2 molecule is paramagnetic. Step2 C2^- has 1 unpaired electron; is also paramagnetic..